I want something similar to "preview" in macs. For example: I want an image editor that ONLY does simple adjustments like increase/decrease contrast, saturation, exposure, color tinting.... rotate, flip vertically, flip horizontally, make black and white, change size or format, crop.

THATS IT. I know gimp can do all those things but its a bit overkill. I just want to right click an image, open it with this magical program i just described, do a few quick adjustments, and then save and exit. Nothing really fancy.

Anyone know of anything like this? Btw I am using ubuntu 12.04 :) It rocks and I am glad I switched from mac, i just need to replace this one piece of software.

Another feature of Pinta is that say you want to continiue a work later on keeping all the layers intact (so that you can add remove them later on) so you can save the file in .ora format. It preserves every edit you have made so that you can reverse the changes.

Shotwell has a single photo view that allows you to do most if not all of what you're asking. Shotwell, of course, has the advantage that it's included by default in modern Ubuntu so there's nothing to install.

To access the Shotwell viewer without separately launching the main Shotwell app, right click the photo and from the Open With menu select Shotwell Photo Viewer:

(You can make the Shotwell viewer the default program to open photos by selecting Properties from the right click menu and messing around in the Open With tab there.)

From the Shotwell viewer, you can rotate, crop, manipulate color levels, etc., and simply save the file when you're done. You can see the tools at the bottom of the window here:

Whereas usually Shotwell is nondestructive (in the sense that any manipulations you perform on photos are only saved to a photo file if you export it), hitting save from the viewer does indeed write the changes to the file.

I would try Pinta (it's in the repos), as it is simple and has all the necessary basic adjustments to do with contrast, brightness, etc, and even has layers functionality. It is ideal for a quick crop, resize or red eye correction. The version in the repos is 1.1, but you can use a ppa from the developers if you want to have a more recent version-see the notes on the site about whether to use the ppa or not. However, the default version is fine and is very useful for those quick corrections. As you can see in the screenshot below the interface is easy to navigate and simple and intuitive to use.

I was just looking for something similar. I've found some candidates on Wikipedia, and I'm about to check some out.

A few I've found so far are: Shotwell, fotoxx, and the already-mentioned gthumb. I don't know yet which ones are in the Ubuntu repository.

EDIT: I have been using Shotwell now for a long time, and find that it does most of what I want, very quickly and easily. When it doesn't, it can directly open a full editor such as GIMP quickly to do the job instead.

I especially like that it can easily resize images, something I do a lot.